Water treating apparatus

ABSTRACT

A method and apparatus are provided for the treatment of water by ion exchange while eliminating leakage. In carrying out the method, water is first passed through a service layer of anion and cation exchange resins in a service zone in the conventional manner. Subsequently, the water is passed through a leakage barrier layer of cation exchange resin in the service zone. Periodically, the resins in the service zone are separated in a separation zone. The anion exchange resin is then regenerated in an anion resin regeneration zone, and the cation exchange resin is regenerated in a cation resin regeneration zone, which preferably also serves as the separation zone. A portion of the cation exchange resin is then transferred to the service zone to establish a leakage barrier layer. The remainder of the cation exchange resin is mixed with the anion exchange resin, and the mixed resins are transferred to the service zone to establish a service layer of anion and cation exchange resins. The invention also provides apparatus for carrying out the method, and requiring only two columns in addition to the service column. These columns include a separation/cation regeneration column and an anion regeneration column. In accordance with the invention, the resin transfer means include leakage barrier resin transfer means for delivering resin from a central portion of the anion regeneration column to the service column to establish a leakage barrier layer of anion exchange resin or of anion plus cation exchange resin.

United States Patent Primary Examiner-Samih N. Zaharna AssistantExaminer-Benoit Castel [57] ABSTRACT A method and apparatus are providedfor the treatment of water by ion exchange while eliminating leakage. incarrying out the method, water is first passed Salem Mar. 12, 1974 WATERTREATING APPARATUS through a service layer of anion and cation exchange[75] Inventor: Eli Salem, Brooklyn NY resins in a service zone in theconventional manner.

Subsequently, the water is passed through a leakage [73] ss gnee UnionTank p y, g barrier layer of cation exchange resin in the service zone.Periodically, the resins in the service zone are [22] Filed: Feb. 25,1971 separated in a separation zone. The anion exchange resin is thenregenerated in an anion resin regenera- [21] Appl. No.: 119,007 tionzone, and the cation exchange resin is regener- Related US ApplicationData ated in a cation resin regeneration zone, which prefer- [62]Division of Ser No 859 042 Sept. 18 I969 Pat. ably als-o Serves as theS-epairanon zone' A porno of NO. 3 585 I27 1 the cation exchange resinis then transferred to the service zone to establish a leakage barrierlayer. The

remainder of the cation exchange resin is mixed with '[58] Field otSearch 210/33 189 transferred. the f estzlblsh a serv'ce layer of anionand cation exchange resins.

[ 56] R f n Cited The invention also provides apparatus for carrying outUNITED STATES PATENTS the method, and requiring only two columns inaddition to the service column. These columns include 2x32; z i s aseparation/cation regeneration column and an anion 3:660:282 5/1972OBrien.... 2l0/l89 regeneratlo column In accmdance the invention, theresin transfer means include leakage barrier resin transfer means fordelivering resin from a central portion of the anion regeneration columnto the service column to establish a leakage barrier layer of anionexchange resin or of anion plus cation exchange resin.

1 Claim, 2 Drawing Figures MI 7 ya //4 WATER TREATING APPARATUS Thisapplication is a division of copending application Ser. No. 859,042,filed Sept. 18, 1969 and now U.S. Pat. No. 3,585,127.

The present invention relates to improvements in the treatment of waterby ion exchange, and more specifically to an improved method andapparatus for treating water by ion exchange while substantiallyeliminating undesirable leakage.

Mixed bed systems containing anion and cation exchange resins for thepurification of water have many industrial applications. A primaryapplication of such a system is in the purification of makeup andcondensate water which is used to drive steam turbines. It is essentialthat this water be of an extremely high purity level in order to avoidany coating on the surfaces of turbine blades, boilers, pipes, etc.Since it is desired to produce water which is free of any residue uponevaporation, the cation exchange resin must be in the hydrogen orammonium form, and the anion exchange resin must be in the hydroxideform. In any event, it is conventional to regenerate the cation exchangeresin with a strong acid such as sulfuric or hydrochloric acid, and toregenerate the anion exchange resin with a strong base, generally sodiumhydroxide. After regeneration, the cation exchange resin may optionallybe converted to the ammonium form. This conversion may be accomplishedby treatment with ammonium hydroxide subsequent to regeneration. Morepreferably, the conversion to the ammonium form simply takes placeduring operation of the steam system, in which ammonium hydroxide isintroduced into the water to prevent corrosion.

A particular problem with mixed bed ion exchange systems of the typeconventionally employed is the production of ion leakage, particularlysodium ion leakage. The term leakage refers to any ions that are notremoved from the water by the ion exchange resin, and thus are permittedto leak past the resin. As used herein, the term leakage also refers toany undesired ions, such as sodium, which are introduced into the waterby the resin itself.

The leakage problem arises primarily from the impossibility of obtainingperfect separation of the anion and cation resins in the mixed bed priorto regeneration. As is familiar to those skilled in the art, suchseparation is conventionally accomplished by passing water through theresin in an upflow direction. This stream of water carries the lessdense anion exchange resins to the top of the separation vessel, whilethe more dense cation exchange resin is permitted to sink to the bottom.While this method is effective in separating the bulk of the resins,perfect separation is not achieved. Furthermore, resin fines will beproduced during use. The cation exchange resin fines will not sink tothe bottom in the separation vessel, but will be carried upwardly withthe anion exchange resin. When the anion exchange resin is subsequentlyregenerated with sodium hydroxide, sodium ions will be introduced intothe ion exchange sites in the cation resin contaminant. When the resinsare returned to the service column, these sodium ions will be exchangedinto the water being treated, producing sodium leakage.

A similar, but less serious, problem arises from the impurity of thecation exchange resin following the separation procedure. The minoramount of anion exchange resin which contaminates the cation exchangeresin will contain sulfate ions when the regenerant is sulfuric acid. Anadditional problem is the silica contained by the anion exchange resin,generally in the form of silicates. This silica is ordinarily removedduring the regeneration process. However, where the anion exchange resinis a contaminant in the cation exchange resin, silica will not beefficiently removed during the regeneration process, and may be carriedover into the water being treated.

Generally, the present invention provides for the treatment of water byion exchange with the elimination of residue-forming cation leakage. Incarrying out the basic process, water is first passed through a servicelayer of anion and cation exchange resins in a service zone in theconventional manner. Subsequently, the water is passed through a leakagebarrier layer of cat ion exchange resin in the service zone.Periodically, the resins in the service zone are separated in aseparation zone. The anion exchange resin is then regenerated in ananion resin regeneration zone, and the cation exchange resin isregenerated in a cation resin regeneration zone, which preferably alsoserves as the separation zone. A portion of the cation exchange resin isthen transferred to the service zone to establish a leakage barrierlayer. Theremainder of the cation exchange'resin is mixed with the anionexchange resin, and the mixed resins are transferred to the service zoneto establish a service layer of anion and cation exchange resins.

The present invention also provides improved apparatus for carrying outthe method of the present invention. This apparatus comprises a servicecolumn, a separation/cation regeneration column, and an anionregeneration column. First resin transfer means are provided fortransferring resin from a service column to the separation/cationregeneration column, while second resin transfer means are provided fordelivering anion exchange resin from the separation/cation regenerationcolumn to the anion regeneration column. Third resin transfer means areconnected for delivery of cation exchange resin from the bottom of theseparation/cation regeneration column to an upper portion of the anionregeneration column. In accordance with the present invention, fourthleakage barrier resin transfer means are provided for delivering centralportion of ion exchange resins from the anion regeneration column to theservice column, in order to establish a leakage barrier layer. Thiscentral portion may include cation or I cation plus anion exchangeresins, depending on the position of the leakage barrier resin transfermeans. Finally, fifth resin transfer means are provided for deliveringthe remaining anion and cationexchange resin from the anion regenerationcolumn to the service column.

The invention will be best understood by reference to the followingdetailed description, taken in conjunction with the drawings, in which:

FIG. 1 is a diagrammatic illustration of an ion exchange system adaptedfor carrying out the method of the present invention; and

FIG. 2 is a diagrammatic illustration of a second ion exchange systemconstructed in accordance with the present invention.

Referring to the drawings, and more particularly to FIG. 1, a suitableapparatus is made up of a number of tanks, generally referred to in theart as columns. In the apparatus of FIG. 1, these columns include aservice column 10, a separation/cation regeneration column 12, an anionregeneration column 14, and a holding column 16. These columns 10, 12,14, 16 define various zones for carrying out the method of the presentinvention. As those skilled in the art will understand, a commercialsystem will usually employ more than one service column for each set ofseparation/cation regeneration, anion regeneration, and holding columns12, 14, 16, respectively. Thus, by replacing the exhausted resin in onlyone service column 10 at a time, the remaining service columns 10 may bekept on stream. However, for simplicity, the system illustrated employsonly a single service column 10, it being understood that the method ofthe present invention is equally well adapted to use with a system whichemploys a multiplicity of service columns 10.

, In normal operation in accordance with the present invention, theservice column 10 contains a service layer 18 of anion and cation resinsand a leakage barrier layer 20. The anion and cation exchange resins inthe service layer 18 will usually be mixed. The leakage barrier layermay be either cation exchange resin or mixed or stratified cation andanion exchange resins, as will hereinafter appear.

An upper transfer pipe 22 is located above the columns 10, 12, 14, 16,and a lower transfer pipe 24 is similarly positioned below the columns.The upper transfer pipe 22 communicates with an upper portion of eachofthe columns 10, 12, 14, 16 through upper connecting pipes 26, 28, 30,32, respectively. Each upper connecting pipe 26, 28, 31), 32 has avalve, indicated respectively by reference numerals 26', 28, 30, 32. Ina similar manner, the lower transfer pipe 24 communicates with a lowerportion of each of the columns 10, l2, 14, 16 through lower connectingpipes 34, 36, 38, 40. Each lower connecting pipe 34, 36, 38, has avalve, indicated respectively by reference numerals 34, 36', 38, 40.

Communication between the upper and lower transfer pipes 22, 24,respectively, is provided by an interconnecting pipe 42. Thisinterconnecting pipe 42 also communicates with a central portion of theseparation/cation regeneration column 12 through an anion resin outletpipe 44 having a valve 44'. As the following description will makeclear, the level at which the anion resin outlet pipe 44 communicateswith the separation/cation regeneration column 12 is important to theproper operation of the apparatus.

The interconnecting pipe 42 has a valve 42 positioned between the uppertransfer pipe 22 and the anion resin outlet pipe 44.

As previously mentioned, separation'of resins in a separation column isconventionally accomplished by an upflow of water, which stratifies theresins in accordance with their densities and particle sizes. In thepresent invention, an upflow of water is introduced into theseparation/cation regeneration column 12 through a water inlet pipe 46,communicating with a lower portion of the column 12, and is withdrawn atan outlet pipe 48 communicating with an upper portion of the column 12.Acid regenerant, such as sulfuric or hydrochloric acid, may beintroduced into the separation/cation regeneration column 12 at aregenerant inlet pipe 50. This regenerant is withdrawn from the column12 through a lower outlet pipe 51.

Anion exchange resin regenerant, generally sodium hydroxide, may bedelivered to the anion regeneration column 14 at a regenerant inlet pipe52 communicating with an upper portion thereof, and is withdrawn at aregenerant outlet pipe 53 communicating with the bottom portion of theanion regeneration column 14. In the preferred embodiment, the anionregeneration column 14 is also equipped with a re-stratification liquidinlet 54, communicating with the bottom thereof, and with an upperoutlet 55.

ln'the event that it is desired to ammoniate the resin, ammoniumhydroxide may be delivered to resin in the holding column 16 through anammonia inlet pipe 56, and withdrawn through a drain 58.

During the service cycle, all valves shown in FIG. 1 are closed. Rawwater from a raw water source enters the service column 10 through a rawwater inlet pipe 60, and passes through the mixed resin layer 18 andthen through the leakage barrier layer 20, wherein any undesired ionssuch as sodium are removed. The purified Water exits from the servicecolumn 10 through a purified water outlet pipe 62.

in order to regenerate the resin while providing a leakage barrier layer20 in accordance with the present invention, the flow of raw water tothe service column 10 is first stopped. The valves 34', 42, 28', locatedrespectively on the lower connecting pipe 34 below the service column10; the interconnecting pipe 42; and the upper connecting pipe 28 abovethe separation/cation regeneration column 12 are opened, and resin fromthe service column 10 is delivered into the top of the separation/cationregeneration column 12. After this resin transfer, the open valves 34',42, 28 are closed. At this point, the service column 10 is ready toreceive a charge of regenerated resins, as hereinafter described.

The mixed resins in the separation/cation regeneration column are nowseparated and stratified by delivering an upflow of water through thecolumn 12 via the water inlet pipe 46 and the outlet pipe 48. Becausethe anion exchange resin is less dense than the cation exchange resin,the anion exchange resin will be carried to the top of the column 12,while the cation exchange resin will remain at the bottom. As usedherein, the term separation refers to bulk classification of anion andcation exchange resins, in accordance with-their differing densities.The term Stratification refers to the individual classification of anionor cation exchange resin in accordance with density, by an up flow ofliquid. Thus, during the separation step, the anion and cation exchangeresins are not only separated, but are also Stratified. That is, thepurest cation exchange resin, which is the least likely to contain anionexchange resin contaminants is at the very bottom, while the purestanion exchange resin is at the very top.

After the resins have been separated in the separation/cationregeneration column 12, the valve 44' on the anion resin outlet pipe 44,the valve 42 on the interconnecting pipe 412, and the valve 30 on theupper connecting pipe 31) above the anion regeneration column 14 areopened, and anion resin is delivered from the separation/cationregeneration column 12 to the anion regeneration column 17. It ispreferred that the anion resin outlet pipe 44 communicate with theseparation/cation regeneration column 12 at a point slightly above thenormal interface between the anion and cation exchange resins. Thisarrangement minimizes the danger of carrying cation exchange resin overwith the anion exchange resin into the anion regeneration column 14.However, it is virtually impossible to completely eliminate thiscarryover, while still obtaining a sufficient quantity of separatedanion exchange resins. Therefore, a small amount of cation exchangeresin will generally be carried over to the anion regeneration column 14along with the anion exchange resin.

Once the above-described transfer of anion exchange resin to the anionregeneration column 14 has been completed, the open valves 44', 42', areclosed.

Although not essential, it is preferred to regenerate the resins in adownflow direction. The cation resin, which remains in theseparation/cation regeneration column 12, is regenerated by downflow ofregenerant delivered to the column 12 through the regenerant inlet pipe50 and removed through the lower outlet pipe 51. As is familiar to thoseskilled in the art, a strong acid such as sulfuric or hydrochloric acidis a suitable regenerant.

At the same time, the anion resin in the anion regeneration column 14 isregenerated by downflow of regenerant, which is delivered through thecolumn 14 via the regenerant inlet pipe 52 and outlet pipe 53. Anystrong base may be employed to regenerate the anion resin, although asolution of sodium hydroxide is generally preferred. Subsequent toregeneration, both the anion and cation exchange resins are rinsed.

in the preferred embodiment of the present invention, the anion exchangeresin in the anion regeneration column 14 is re-stratified by anupwardly flowing stream of liquid, so that cation exchange resinimpurities will sink to the bottom. The re-stratification isaccomplished by passing a stream of liquid upwardly through the anionregeneration column 14, and may take place before or after theregeneration. Re-- stratification may also be performed after therinsing step. The liquid enters the column 14 at the restratificationliquid inlet 54, and is removed via the upper outlet 55.Re-stratification is important if it is desired to provide anionexchange resin in the leakage barrier layer 20, and/or if the bottomportion of the anion exchange resin is to be returned to theseparation/cation regeneration column, as hereinafter described.

As a result of the separation step, the cation exchange resin (which hasnot been moved) is already properly stratified. However, in a systemwhere the cation exchange resin has been moved, or where significantagitation has occurred, the cation exchange resin may also bere-stratified at this time.

The bottom portion of the cation exchange resin in the separation/cationregeneration column 12 is now transferred to the holding column 16 byopening the valves 36, 40' on the lower connecting pipes 36, 40 belowthe separation/cation regeneration and holding columns 12, 16,respectively. Because only the bottom portion of the stratified cationexchange resin in the separation/cation regeneration column 12 istransferred, this portion will be least likely to contain any anionexchange resin. In the preferred embodiment, approximately fifty percent of the cation exchange resin is transferred from theseparation/cation regeneration column 12 to the holding column 16 inthis step. The cation exchange resin in the holding column 16 willeventually be employed as a leakage barrier layer v20 in the servicecolumn 10.

If it is not desired to provide a leakage barrier layer 20 containinganion exchange resin, the valve 40 on the lower connecting pipe 40 belowthe holding column 16 is closed, and the valves 42', 30' on theinterconnecting pipe 42 and the upper connecting pipe 30 above the anionregeneration vessel, respectively, are opened. The remainder of thecation exchange resin in the separation/cation regeneration column 12 isnow delivered to the anion regeneration column 14 via the lowerconnecting pipe 36 below the separation/cation regeneration column 12,the interconnecting pipe 42, and the upper connecting pipe 30 above theanion regeneration column 14. At the end of this step, all valves areclosed.

On the other hand, ifit is desired to include anion exchange resin inthe leakage barrier layer 20, the cation exchange resin is nottransferred to the anion regeneration column 14 at this time. lnstead,all valves are closed subsequent to the transfer of cation exchangeresin to the holding column 16, as described above. An upper portion(generally about 50 percent) of the stratified anion exchange resin isthen withdrawn from the anion regeneration column 14 via an anion resintransfer pipe 64 having a valve 64. The valves 42', 32' on theinterconnecting pipe 42 and the upper connecting pipe 32 are alsoopened, so that the anion exchange resin enters the holding column 16 atthe top. Thus, in this instance, the holding column 16 will contain alower layer of anion exchange resin and an upper layer of cationexchange resin, both in a highly regenerated, highly purified state. Atthe end of this step, all valves are closed.

If it is desired to ammoniate the resin, an ammonium hydroxide solutionis delivered to the resin in the holding column 16 through the ammoniainlet pipe 56. Although the ammonia may be withdrawn through the drain58, in the preferred embodiment the ammonia is then conducted throughthe resins in the anion regeneration column 14, so that the resins inthe two columns 14, 16 are ammoniated in series, the leakage barrierlayer in the holding column 16 being ammoniated first.

in the most preferred embodiment of the present invention, prior to theintroduction of cation exchange resin into the anion regeneration column12, the anion exchange resin in the anion regeneration column 14 willhave been backwashed and re-stratified in the manner previouslydescribed, so that most of the entrained cation exchange resin (whichwill now be in the sodium form) will settle to the bottom. This minor,bottom portion is now transferred from the anion regeneration column 14back to the separation/cation regeneration column 12 via the lowertransfer pipe 24 and the lower connecting pipes 36, 38 below theseparation/cation regeneration column 12 and the anion regenerationcolumn 14, respectively. This step insures the virtually completeremoval of any cation exchange resin that may have been carried overfrom the separation/cation regeneration column 12 with the anionexchange resin during the initial transfer.

The separation/cation regeneration column 12 is now ready to receive acharge of exhausted resins from another service column 10 in the mannerpreviously described. The regenerated cation exchange resin or cationplus anion exchange resin in the holding column 16 is now transferred tothe service column 10 to form a lower leakage barrier layer. Thistransfer may be ac-- complished through the lower connecting pipe 40below the holding column 16, the lower transfer pipe 24, theinterconnecting pipe 42, the upper transfer pipe 22, and the upperconnecting pipe 26 above the service column 10. i

The anion and cation exchange resins in the anion regeneration column 14may be mixed together, and are then transferred to the service column 10through the lower connecting pipe 38, these mixed resins following thesame route as the leakage barrier resins to the service column 10. Whendelivered to the service column 10, these mixed resins from the anionregeneration column 14 form a mixed resin layer 18 above the leakagebarrier layer 20.

FIG. 2 shows an embodiment of the present invention that is particularlywell adapted to the provision of a leakagebarrier layer containing bothanion and cation exchange resins. This method and apparatus has theparticular advantage that only two columns in addition to the servicecolumn(s) are required for a complete system, rather than three asrequired in the system shown in FIG. 1.

The embodiment illustrated in FIG. 2 comprises a service column 70, aseparation/cation regeneration column 72, and an anion regenerationcolumn 74. As with the apparatus of FIG. 1, the service column 70defines a service zone, the separation/cation regeneration column 72defines separation and cation regeneration zone, and the anionregeneration column 74 defines an anion regeneration zone. Duringoperation, the service column 70 contains an upper service resin layer76 and a lower leakage barrier layer 78. The upper layer 76 containsboth anion'and cation exchange resins, while the lower layer 78 maycontain cation or cation plus anion exchange resins.

As with the embodiment shown in FIG. 1, an upper transfer pipe 80 islocated above the columns 70, 72, 74, and a lower transfer pipe 82 islocated below the columns. The upper transfer pipe 80 communicates withan upper portion of each of the columns 70, 72, 74 through upperconnecting pipes 84, 86, 88, respectively. Each upper connecting pipe84, 86, 88 has a valve indicated respectively by reference numerals 84',86, 88. In a similar manner, the lower transfer pipe 82 communicateswith a lower portion of each of the columns 70, 72, 74 through lowerconnecting pipes 90, 92, 94. Each lower connecting pipe 90, 92, 94, hasa valve, indicated respectively by reference numerals 90, 92', 94.

Communication between the upper and lower transfer pipes 80, 82,respectively, is provided by an interconnecting pipe 96. Thisinterconnecting pipe 96 also communicates with a central portion of theseparation/cation regeneration column 72 through an anion resin outletpipe 98 having a valve 98. As with the embodiment shown in FIG. 1, thelevel at which the anion resin outlet pipe 98 communicates with theseparation/cation regeneration column 72 is important to the properoperation of the apparatus. The interconnecting pipe 96 has a valve 96positioned between the uppertransfer pipe 80 and the anion resin outletpipe 98.

In accordance with the present invention, a leakage barrier transferpipe 100 having a valve 100' communicates with a central portion of theanion regeneration column 74..

As with the embodiment shown in FIG. 1, the separation/cationregeneration column 72 is provided with a water inlet pipe 102, an upperoutlet pipe 104, and a regenerant inlet pipe 105, and a lower outletpipe 106. The water inlet pipe 102 and lower outlet pipe 106 communicatewith the bottom of the separation/cation regeneration column 72, whilethe upper outlet pipe 104 and regenerant inlet pipe 105 communicate withthe top of the column 72.

The anion regeneration column 74 is equipped with a re-stratificationliquid inlet pipe 108, regenerant inlet pipe 110, and upper outlet pipe111 and a lower outlet pipe 112. The re-stratification liquid inlet pipe108 communicates with the bottom of the anion regeneration column 74,while the regenerant inlet and upper outlet pipes 110, 111,respectively, communicate with the top.

In operation, raw water is delivered downwardly through the servicecolumn via a raw water inlet 113, and removed at a lower purified wateroutlet 114. The water therfore passes first through the service layer 76and then through the leakage barrier layer 78. When it is desired toregenerate the resin in the service column 70, the flow of raw water tothe raw water inlet 113 is halted.

Exhausted resin from the service column 70 is transferred to theseparation/cation regeneration column 72 through the lower connectingpipe 90, below the service column 70, the lower transfer pipe 82, theinterconnecting pipe 96, the upper transfer pipe 80, and the upperconnecting pipe 86 above the separation/cation regeneration column 72.The resins are then separated in the separation/cation regenerationcolumn 72 by an upflow of water delivered through the water inlet pipe102, and removed through the outlet pipe 104. After separation, themajority of the anion exchange resin is transferred to the anionregeneration column 74 via the anion resin outlet pipe 98, theinterconnecting pipe 96, the upper transfer pipe 80, andthe upperconnecting pipe 88 above the anion regeneration column 74. The anion andcation exchange resins are then regenerated by suitable regenerantsdelivered through the regenerant inlet pipes 105, 110, and removed atthe lower outlet pipes 106, 112. The anion exchange resin in the anionregeneration column 74 is also re-stratified by an upwardly flowingliquid, which may be delivered to the column 74 through there-stratification liquid inlet pipe 108. This re-stratification willplace the purest anion exchange resin uppermost, the more dense cationexchange resin contaminant sinking to the bottom.

It will be noted that up to this point the operation of the apparatus ofFIG. 2 is the same as the operation of the apparatus of F IG. 1.

After the re-stratification of the anion exchange resin valves 92', 96',and 88' are opened, providing communication between the bottom of theseparation/cation regeneration column 72 and the top of the anionregeneration column 74. The cation exchange resin is delivered to theanion resin regeneration column. During this delivery, the resin at thebottom of the separation/- cation regeneration column 72 will bedelivered first, so that it will also be on the bottom in the anionregeneration column 74, just above the anion exchange resin. The anionexchange resin in the anion regeneration'column 74 is designated byreference numeral 115, and the cation exchange resin is designated byreference numeral 1 16. At the end of this step, all valves are closed.

At this point, in accordance with the preferred embodiment, a bottomportion of the resins in the anion regeneration column 74 is transferredto the separation/cation regeneration column by opening the valves 94,92' on the lower connecting pipes 94, 92 below the anion regenerationand separation/cation regeneration columns 74, 72, respectively. Becausethe anion exchange resin has been re-stratified, most of the sodiumformcation exchange resin contaminant will have sunk to the bottom. Thisstep therefore insures the virtually complete removal of any cationexchange resin that may have been carried over from theseparation/cation regeneration column 72 during the initial transfer. Atthe end of the foregoing step, the open valves 92', 94' are closed.

If it is desired to ammoniate the resin, ammonium hydroxide is delivereddownwardly through the anion regeneration column 74 via the regenerantinlet pipe 1 10, and is withdrawn at the lower outlet pipe 112.

Because of the way the resins have been handled, the purest cationexchange resin will be on the bottom, i.e., at the interface, while thepurest anion exchange resin 115 will be at the top, i.e., also at theinterface. It is therefore clear that the purest anion and cationexchange resins form the central portion of the anion and cationexchange resins in the anion regeneration column 74. It is noted thatwhen the leakage barrier transfer pipe 100 communicates with the anionregeneration column 74 below the interfacial level of the two resins,some anion resin will be first collected, and then, as the level falls,cation resin will be collected and delivered to the service column 70.If it is not desired to include anion exchange resin in the leakagebarrier layer 78, the leakage barrier transfer ,pipe 100 is positionedto communicate with the anion regeneration column 74 just above theinterface between the two resins 115, 116.

The position of the leakage barrier transfer pipe also determines theamount of anion exchange resin that can be delivered to the leakagebarrier layer 78. That is, the lower the pipe, the more anion exchangeresin delivered. Where it is desired to include anion exchange resin inthe leakage barrier layer, the leakage barrier transfer pipe 100 shouldpreferably be positioned to transfer about fifty per cent of the anionexchange resin 115 to the service column 70.

Once sufficient resin has been delivered to the service column 70 toform a leakage barrier layer 78, the valve 100 on the leakage barriertransfer pipe 100 is closed. The remainder of the anion and cationexchange resins in the anion regeneration column 74 may optionally bemixed, and these resins are then transferred to the service column 70via the lower transfer pipe 82, the interconnecting pipe 96, and theupper transfer pipe 80, so that the mixed resins form an upper servicelayer 76 above the leakage barrier 78 within the service column 70.

As those skilled in the art will realize, resin transfer in theapparatus shown in FIGS. 1 and 2 may be accomplished by any one ofanumber of means, not shown in the drawings. For example, resin transfermay be accomplished by the use of air and water pressure, water pressurealone, pumps, and the like, the resin generally being handled in anaqueous suspension.

The method of the present invention is adaptable to use with a widevariety of anion and cation exchange resins, so long as they differ indensity when exhausted a sufficient amount to permit them to beseparated in the separation/cation regeneration columns 12, 72. Typicalsolid cation exchange resins which may be employed in the presentinvention are those of the divinylbenzene-styrene copolymer type, theacrylic type, the sulfonated coal type, and the phenolic type. Typicalsolid anion exchange resins that may be employed in the presentinvention are the phenol-formaldehyde type, the divinylbenzenestyrenecopolymer type, the acrylic type, and the epoxy type. The anion andcation resins are both preferably employed as beads in the size range ofabout 16-60 mesh. Suitable bead resins are sold under the trade namesAmberlite, manufactured and sold by Rohm & Haas Company, and Nalcoresins sold by Nalco Chemical Company. Particularly suitable ionexchange resins are sold under the trade names Amberlite IRA-900 andIRA-400 (anionic); and [RA- 200 and IRA- (cationic). v

Obviously, many modifications may be made in the precise manner in whichthe method of the present invention is carried out. For example, by asuitable adjustment of the operation, the anion resin may be regeneratedin the separation/regeneration column 12 while the cation regenerationis transferred to the column 14 for regeneration. If it were desired tooperate the service column 10 in an upflow rather than a downflowdirection, the method of the present invention could be easily adaptedto provide the leakage barrier 20 as the upper, rather than lower, layerin the service column 10.

Those skilled in the art will also understand that virtually an infinitevariety of piping systems may be employed in order to carry out themethod of the present invention. While those piping systems shown inFIGS. 1 and 2 are preferred, a number of equally workable systems couldbe provided without departing from the spirit and scope of the presentinvention.

By the same token, a number of routes can be used to transfer resin withthe apparatus shown in the drawings. While the routes set forth in theforegoing detailed description are at present considered preferred,those skilled in the art will realize that numerous variations may bemade within the spirit and scope of applicants invention. Many moremodifications and variations will obviously occur to those skilled inthe art, and all such modifications and variations fall within the truespirit and scope of the invention.

1 claim:

1. Improved apparatus for treating water by ion exchange comprising: aservice column; a separation/cation regeneration column; an anionregeneration column having a top, a bottom and a central portion; meansto feed water to be purified into said service column, and means todischarge purified water from said service column; stratification meansto separate anion and cation resins in the separation/cationregeneration column into separate layers, and regeneration means toregenerate the cation resin in said separation/cation regenerationcolumn; means to regenerate the anion resin in said anion regenerationcolumn, and restratification means in said anion regeneration column;first resin transfer means for transferring resin from said servicecolumn to said separation/cation regeneration column; second resintransfer means for delivering anion 12 tion column for delivering resinfrom said central portion of said anion regeneration column to saidservice column; and fifth resintransfer means for delivering resin froma lower portion of said anion regeneration column to said servicecolumn.

' UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,796,319 ,Dated March 12; 1974 Inventor(s) ELI SALEM It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below;

In t ne cover sheet, after "Asignee" delete Union Tank Car Company,Chicago, Ill." and insert --E codyne Corporation, Chicago, Illinois".

Signedand sealed this 8th day of October 1974.

(SEAL) Attest:

MCCOY M. G IBSON JR. c. MARSHALLDANN Attesting Offic'er Commissioner ofPatents

1. Improved apparatus for treating water by ion exchange comprising: a service column; a separation/cation regeneration column; an anion regeneration column having a top, a bottom and a central portion; means to feed water to be purified into said service column, and means to discharge purified water from said service column; stratification means to separate anion and cation resins in the separation/cation regeneration column into separate layers, and regeneration means to reGenerate the cation resin in said separation/cation regeneration column; means to regenerate the anion resin in said anion regeneration column, and restratification means in said anion regeneration column; first resin transfer means for transferring resin from said service column to said separation/cation regeneration column; second resin transfer means for delivering anion exchange resin from said separation/cation regeneration column to said anion regeneration column; third resin transfer means for delivering cation exchange resin from the bottom of said separation/cation regeneration column to an upper portion of said anion regeneration column; fourth resin transfer means connected directly to said central portion of the anion regeneration column for delivering resin from said central portion of said anion regeneration column to said service column; and fifth resin transfer means for delivering resin from a lower portion of said anion regeneration column to said service column. 